MC33187

This is the standard operation of this circuit requiring the minimum of extra components.The ON/OFF switch is a non-latching push button (or similar), illuminated by a lamp in parallel with the rear window defogger. Rin protects the toggle input from supply line transients with a nominal of Rin = 10K. The relay is intended to be a standard automotive relay (Rnom = 60) with contacts rated appropriately for the defogger controlled. Dz with a nominal value of 16V +-5% is included to provide protection of the relay drive output transistor against relay turn-off and supply lines transients.

The type of zener used is dependent of the level of protection required. An MZD16 will provide adequate protection for all relay turn-off and low energy supply transients, while a P6KE16A will provide full protection against all known transients. If the relay output is to be connected in any other way or to a non-standard relay, the maximum ratings quoted under the General Description above should be noted.

MC33187 is a Long Duration Automotive Timer primarily designed as a deffoger timer, but as it is realised using a digital divider techniques and it is suitable for a variety of long duration timing functions. The MC33187 is available in an 8 pin surface plastic package.
• Operating Ambient Temperature from -40°C to 85°C
• Operating Voltage Range from 5V to 18V
• 400mA Output Current Capability
• Integrated Input Debounce Circuitry
• Few External Components
• Toggle Input for Timing Start and Stop